firmwareLinuxNonfree: simplify source fetching

The iwlwifi repo has been merged into linux-firmware.

pkgs/os-specific/linux/firmware/firmware-linux-nonfree/default.nix

@@ -2,51 +2,12 @@
 
 stdenv.mkDerivation rec {
   name = "firmware-linux-nonfree-${version}";
-  version = "2018-03-20-${src.iwlRev}";
+  version = "2018-03-20";
 
-  # The src runCommand automates the process of building a merged repository of both
-  #
-  # https://git.kernel.org/cgit/linux/kernel/git/firmware/linux-firmware.git/
-  # https://git.kernel.org/cgit/linux/kernel/git/iwlwifi/linux-firmware.git/
-  #
-  # This gives us up to date iwlwifi firmware as well as
-  # the usual set of firmware. firmware/linux-firmware usually lags kernel releases
-  # so iwlwifi cards will fail to load on newly released kernels.
-  #
-  # To update, go to the above repositories and look for latest tags / commits, then
-  # update version to the more recent commit date
-
-  src = runCommand "firmware-linux-nonfree-src-merged-${version}" {
-    shallowSince = "2017-10-01";
-    baseRev = "44476f2465dac9c22bce90da66e86b2b56ba34f0";
-    iwlRev = "iwlwifi-fw-2018-03-02";
-
-    # When updating this, you need to let it run with a wrong hash, in order to find out the desired hash
-    # randomly mutate the hash to break out of fixed hash, when updating
-    outputHash = "1gh5a2km33jj151j3q7mgkjzzhaaxlqxbb53n4ff46q658gv0wma";
-
-    outputHashAlgo = "sha256";
-    outputHashMode = "recursive";
-
-    # Doing the download on a remote machine just duplicates network
-    # traffic, so don't do that.
-    preferLocalBuild = true;
-
-    nativeBuildInputs = [ cacert git gnupg ];
-  } ''
-    git init src && (
-      cd src
-      git config user.email "build-daemon@nixos.org"
-      git config user.name "Nixos Build Daemon $name"
-      git remote add base https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git
-      git remote add iwl https://git.kernel.org/pub/scm/linux/kernel/git/iwlwifi/linux-firmware.git
-      git fetch --shallow-since=$shallowSince base
-      git fetch --shallow-since=$shallowSince iwl
-      git checkout -b work $baseRev
-      git merge $iwlRev)
-    rm -rf src/.git
-    cp -a src $out
-  '';
+  src = fetchgit {
+    url = "https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git";
+    sha256 = "1gh5a2km33jj151j3q7mgkjzzhaaxlqxbb53n4ff46q658gv0wma";
+  };
 
   preInstall = ''
     mkdir -p $out